SKSpriteNode disappear in GameScene - ios

Question

I'm facing some problem with spritekit in swift.
I was following closely to online tutorials (combining different tutorials into 1 project), trying out the code when I realised my SKSpriteNodes (my "player" and "enemy") sometimes go missing when I try it out on simulator or my iphone.
My situation is kinda similar to this user's problem here, but I don't think my problem lies with the size.
Can anyone enlighten me? Thank you!
Here's my code.
var player : SKSpriteNode!
var backdrop : SKSpriteNode!
var gameTimer : Timer!
var possibleEnemies = ["enemy01", "enemy02", "enemy03"]
let bulletsCategory : UInt32 = 0x1 << 0
let enemyCategory : UInt32 = 0x1 << 1
override func didMove(to view: SKView) {
player = SKSpriteNode(imageNamed: "bird.png")
player.position = CGPoint(x: 0, y: (player.size.height / 2) )
self.addChild(player)
self.physicsWorld.gravity = CGVector(dx: 0, dy: 0)
self.physicsWorld.contactDelegate = self
self.anchorPoint = CGPoint (x: 0.5 , y: 0)
createBackdrop()
scoreLabel = SKLabelNode(text: "Score: 0")
scoreLabel.position = CGPoint(x: 260, y: self.frame.size.height - 90)
scoreLabel.fontName = "Avenir Book"
scoreLabel.fontSize = 35
scoreLabel.fontColor = UIColor.gray
score = 0
self.addChild(scoreLabel)
gameTimer = Timer.scheduledTimer(timeInterval: 0.75, target: self, selector: #selector(addEnemies), userInfo: nil, repeats: true)
}
#objc func addEnemies() {
possibleEnemies = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: possibleEnemies) as! [String]
let enemy = SKSpriteNode(imageNamed: possibleEnemies[0])
let randomEnemyPosition = GKRandomDistribution(lowestValue: -360, highestValue: 360)
let position = CGFloat(randomEnemyPosition.nextInt())
enemy.position = CGPoint(x: position, y: self.frame.size.height + enemy.size.height)
enemy.physicsBody = SKPhysicsBody(rectangleOf: enemy.size)
enemy.physicsBody?.isDynamic = true
enemy.physicsBody?.categoryBitMask = enemyCategory
enemy.physicsBody?.contactTestBitMask = bulletsCategory
enemy.physicsBody?.collisionBitMask = 0
self.addChild(enemy)
let animationDuration : TimeInterval = 6
var actionArray = [SKAction]()
actionArray.append(SKAction.move(to: CGPoint(x: position, y: -enemy.size.height), duration: animationDuration))
actionArray.append(SKAction.removeFromParent())
enemy.run(SKAction.sequence(actionArray))
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
fireBullets()
}
func fireBullets() {
self.run(SKAction.playSoundFileNamed("shoot.wav", waitForCompletion: false))
let bullets = SKSpriteNode(imageNamed: "bullet.png")
bullets.position = player.position
bullets.position.y += 5
bullets.physicsBody = SKPhysicsBody(rectangleOf: bullets.size)
bullets.physicsBody?.isDynamic = true
bullets.physicsBody?.categoryBitMask = bulletsCategory
bullets.physicsBody?.contactTestBitMask = enemyCategory
bullets.physicsBody?.collisionBitMask = 0
bullets.physicsBody?.usesPreciseCollisionDetection = true
self.addChild(bullets)
let animationDuration : TimeInterval = 0.3
var actionArray = [SKAction]()
actionArray.append(SKAction.move(to: CGPoint(x: player.position.x, y: self.frame.size.height + 10), duration: animationDuration))
actionArray.append(SKAction.removeFromParent())
bullets.run(SKAction.sequence(actionArray))
}
func didBegin(_ contact: SKPhysicsContact) {
var firstBody : SKPhysicsBody
var secondBody: SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
if (firstBody.categoryBitMask & bulletsCategory) != 0 && (secondBody.categoryBitMask & enemyCategory) != 0 {
hitByBullets(bulletNode: firstBody.node as! SKSpriteNode, enemyNode: secondBody.node as! SKSpriteNode)
}
}
func hitByBullets (bulletNode: SKSpriteNode, enemyNode: SKSpriteNode) {
let shot = SKEmitterNode(fileNamed: "Magic01")!
shot.position = enemyNode.position
self.addChild(shot)
self.run(SKAction.playSoundFileNamed("shot.mp3", waitForCompletion: false))
bulletNode.removeFromParent()
enemyNode.removeFromParent()
self.run(SKAction.wait(forDuration: 2)) {
shot.removeFromParent()
}
score += 1
}
func touchDown(atPoint pos : CGPoint) {
player.position = pos
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for t in touches { self.touchDown(atPoint: t.location(in: self)) }
}
override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
moveBackdrop()
}

Answer 1

the issue for you sprites not showing up is that none of your objects have a zPosition set on them. You need to layer the objects as you expect them to show in the scene.
for example...
background.zPosition = 1
player.zPosition = 1
enemy.zPosition = 1
bullet.zPosition = 2
scoreLabel.zPosition = 100
In my opinion you shouldn't be using timers to generate your enemies. Spritekit has it's own timing functionality built into the update function. Which you are already using to control the timing of the backgrounds.
You had waaaaay to much code in your question, you need to look at how I've tailored the code down to only relevant code to your question. Including all of your code in your question actually makes it more unlikely that you will get the help or answers you need because it is harder to go through all the code to figure out what is happening. Also don't include so many spaces in your code in your question scrolling through hundreds of lines even if a lot of them are spaces is very tedious.

Answer 2

Didn't realised the importance of zPosition since my items show up perfectly on screen some of the times. Added the following in their respective place and they stop disappearing intermittently.
player.zPosition = 3
scoreLabel.zPosition = 100
enemy.zPosition = 3
bullets.zPosition = 2
backdrop.zPosition = 1
shot.zPosition = 3